A Perfect Ambush

When this unit is set up on the battlefield as Reinforcements as a result of being set up underground (pg 88), you can use this ability. If you do, select one enemy unit within 12" of this unit. Until the end of the turn, each time a model in this unit makes a ranged attack against that enemy unit, that enemy unit is treated as having a crossfire marker and as being Exposed (pg 89) for that attack.